ISSI TEAM

Light Scattering Phenomena in Small Body Surfaces

Cellino, A. (Italy), Belskaya, I. N. (Ukraine), Delbó, M. (Italy), Levasseur-Regourd, A.C. (France), Muinonen, K. (Finland),

Tedesco, E. F. (USA)

The goal of this project is to develop an interdisciplinary approach to attack a few well defined problems of major interest involving phenomena of light scattering by surfaces of atmosphereless solar system bodies. This is a timely and urgent task, due to the fact that further advances in the interpretation of remote sensing observations of asteroids and other small solar system bodies from the ground and from space, including ESA’s Gaia mission, are urgently in need of an improved understanding of light scattering phenomena.

An urgent task in asteroid science is the derivation of a new, updated calibration of the relation between the albedo of the objects and the observable properties of the state of polarization of their reflected light. Asteroid polarimetry is one of the best available techniques for deriving asteroid albedos, but its full potential is currently hampered by insufficient knowledge of some important calibration constants. New observations and theoretical efforts are needed to improve this situation, and the present proposal is aimed at obtaining some decisive results in this respect. We note that the Rosetta space probe will perform two flybys with asteroids (2867) Steins and (21) Lutetia in 2008 and 2010, respectively; a very nice opportunity to test updated theoretical expectations, taking also into account that these two objects do not belong to the most usual asteroid taxonomic classes, and/or are known to exhibit unusual polarimetric properties. We also want to attack the problem of the large errors, up to 0.5 mag, known to affect the listed values of asteroid absolute magnitudes, which has serious consequences for our ability to derive accurate asteroid sizes and albedoes. The solution to this problem is directly related to a better understanding of the laws of variation of the apparent brightness under different illumination conditions, a classical problem of light scattering. 

Commission 15 of the IAU has recently appointed two Task Groups devoted to finding solutions to the above problems. The authors of this proposal represent a major fraction of the members of these two Task Groups. These activities will be also very important in the framework of the Gaia mission, for which a critical difficulty in deriving extremely accurate orbits and physical properties of thousands of asteroids will be to correctly compute the “photocenter shift”, a phenomenon in which light scattering plays a crucial role.

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Last modified: Saturday, 28 July 2007 by E. Tedesco